The invention relates generally to devices for slowing and stopping movable machine elements, particularly those devices which embody energy absorption elements. The invention is broadly applicable to movable robot platforms or bases, and is especially applicable to rotatable robot platforms having a bi-directional range of movement of less than 360.degree..
Many industrial robots, including the articulated arm types and coordinately movable slide systems, are supported on a rotatable platform which, in turn, is typically journalled on a fixed robot base to provide the system with a rotary axis of movement. The rotatable platform is power driven from the fixed base and is typically positioned in response to a signal generated by a position sensing element such as an encoder or resolver affixed to the drive system. Maximum end-of-travel stops are provided to limit the platform travel.
If a rotatable platform is stopped in its movement by rigid stopping elements, the shock may result in deleterious conditions. For example: workpieces may be jostled in their respective grippers; the drive train may be damaged; and loosening of robotic components may occur.
Energy-absorbing snubbers and shock absorbers are well-known in machine fields, and a typical design involves a piston and cylinder coacting against a fluid interface in much the same manner as the action of an automobile shock absorber applied between the body and frame. Prior art shock absorbers have certain disadvantageous features; for example: loss of effectiveness due to seal wear; fluid leakage in hydraulic devices; linear stroke and relatively long dimensions in both pneumatic and hydraulic devices; certain rubber bumpers are contacted directly and tend to degrade quickly. Additionally, the prior art devices are generally unidirectional in function.
In contrast to the prior art devices, applicant has conceived a novel mechanical stop device for arresting movement of a robotic platform where the stop embodies shock-absorbing and controlled deceleration characteristics and, secondarily, provides for stopping of overtravel in the event of rapid degradation of the cushion element. The stop is also configured to act against bi-directional rotary movement.
It is therefore an object of the present invention to provide a compact, simplified, cushioned stop for a movable robotic platform.
Another object of the present invention is to provide a mechanical cushioned stop for a robotic platform which is relatively trouble-free and maintenance-free.
A further object of the invention is to provide a mechanical robotic platform stop having controlled deceleration characteristics.